Protecting the river from the rooftops

Comprising up to 26 percent of urban areas, rooftops are a prominent, but often underused element of modern architecture. According to Michigan State University's green roof research team, greenery can enhance the durability of these structures, reduce the quantity of stormwater runoff, and act as a natural filtration system to cleanse runoff before it reaches waterways like our very own Red Cedar River.

Initiated in collaboration with Ford Motor Company in 2000, MSU's green roof team was assembled to advise the automobile giant on incorporating green roofs into construction of a new assembly plant at the Rouge Complex in Dearborn, Michigan. "They had a lot of concerns about stormwater runoff carrying pollutants into the river," said lead green roof researcher and professor in MSU's Department of Horticulture, Brad Rowe, "but instead of abandoning the site, they used green roofs, porous pavement and retention ponds to help reduce runoff and naturally clean the area."

Continued funding from this partnership allows the team to investigate various installations, applications and uses for green roofs, using campus as a laboratory for research by top faculty members and students. Areas of research vary widely, from carbon sequestration and microclimate moderation to pollution, public awareness and wildlife habitat relationships. Rowe and his team currently manage eight green roofs on campus in addition to numerous smaller research plots.

"The campus green roofs are a great research tool," said Rowe, "they allow us to track things like roof temperature and growth of different plants. On the Plant and Soil Sciences Building green roof alone, we've been monitoring the long-term growth of 16 different plant species for 13 years."

In addition, Rowe regularly works with graduate and undergraduate students on smaller research projects that address industry challenges. Currently, the team is investigating a unique solution to "growing media," an engineered soil used on green roofs that mimics the properties of natural soil, but weighs less and helps better manage moisture within a roof drainage system. Traditionally, the material is made of heat-expanded slate or shale, which works well but requires a lot of energy to produce.

Rowe's idea: crush waste porcelain into small pieces and use it as one of the components for the engineered soil, removing some of the energy demand. "It wasn't as good as traditional product, but the results were promising," said Rowe, "I think we can make some educated adjustments and see more success, starting by crushing the material into finer particle sizes. We're definitely moving in the right direction."

While the team is constantly learning how to make green roofs more accessible and sustainable for modern consumers, the benefits of installing them can already be seen on campus. "Because we have a utility system that drains stormwater from the rain into the Red Cedar River, it's our responsibility to manage the flow, pollutants and sediment that could get into that system," said Dave Wilber, Landscape Architect with MSU Infrastructure Planning and Facilities, "utilizing stormwater management tools like green roofs and rain gardens helps protect the river from downstream flooding and keeps the water clean for existing wildlife."

Both Rowe and Wilber anticipate that the amount of green roofs and other green infrastructure on campus and in municipal communities will increase in the future, despite challenges in installation, as they present both economic and environmental value. "Cost is always a factor with the installation of green roofs," said Wilber, "however, if we didn't use tools to naturally filter stormwater and slow down the flow process, the environmental cost would be extremely high, so it's absolutely necessary."

Research has also demonstrated that green roofs have benefits beyond stormwater management. "Not only do green roofs reduce the overall temperature of roofs in the summer and help keep heat in during the winter, but they also stabilize the constant dips and peaks in temperature throughout the year," said Rowe, "reducing the freezing and heating of a roof ultimately reduces the risk for cracks, which can extend the life of a roof to last up to 60 years." Rowe also added that extending the life of roofs reduces the waste deposited in landfills and the demand for new roofing.

As communities across the world address growing infrastructure issues, green roofs and other green infrastructure are proving successful in reclaiming lost greenspace, reducing building costs, and filtering runoff and pollution from stormwater. For Rowe, all signs point to progress in the future. "15 years ago, hardly anyone knew what green roofs were, but now my students are coming in prepared with knowledge about the concept. It's clear the industry is already changing, and we're excited to be part of it."